Prolonged monitoring of esophageal motor function in healthy children

Circadian Rhythms and Melatonin Metabolism in Patients With Disorders of Gut-Brain Interactions

Circadian rhythms are cyclic patterns of physiological, behavioural and molecular events that occur over a 24-h period. They are controlled by the suprachiasmatic nucleus (SCN), the brain’s master pacemaker which governs peripheral clocks and melatonin release. While circadian systems are endogenous, there are external factors that synchronise the SCN to the ambient environment including light/dark cycles, fasting/fed state, temperature and physical activity. Circadian rhythms also provide internal temporal organisation which ensures that any internal changes that take place are centrally coordinated. Melatonin synchronises peripheral clocks to the external time and circadian rhythms are regulated by gene expression to control physiological function. Synchronisation of the circadian system with the external environment is vital for the health and survival of an organism and as circadian rhythms play a pivotal role in regulating GI physiology, disruption may lead to gastrointestinal (GI) dysfunction. Disorders of gut-brain interactions (DGBIs), also known as functional gastrointestinal disorders (FGIDs), are a group of diseases where patients experience reoccurring gastrointestinal symptoms which cannot be explained by obvious structural abnormalities and include functional dyspepsia (FD) and irritable bowel syndrome (IBS). Food timing impacts on the production of melatonin and given the correlation between food intake and symptom onset reported by patients with DGBIs, chronodisruption may be a feature of these conditions. Recent advances in immunology implicate circadian rhythms in the regulation of immune responses, and DGBI patients report fatigue and disordered sleep, suggesting circadian disruption. Further, melatonin treatment has been demonstrated to improve symptom burden in IBS patients, however, the mechanisms underlying this efficacy are unclear. Given the influence of circadian rhythms on gastrointestinal physiology and the immune system, modulation of these rhythms may be a potential therapeutic option for reducing symptom burden in these patients.

Review of paediatric gastrointestinal physiology relevant to the absorption of orally administered medicines

Despite much progress in regulations to improve paediatric drug development, there remains a significant need to develop better medications for children. For the design of oral dosage forms, a detailed understanding of the specific gastrointestinal (GI) conditions in children of different age categories and how they differ from GI conditions in adults is essential. Several review articles have been published addressing the ontogeny of GI characteristics, including luminal conditions in the GI tract of children. However, the data reported in most of these reviews are of limited quality because (1) information was cited from very old publications and sometimes low quality sources, (2) data gaps in the original data were filled with textbook knowledge, (3) data obtained on healthy and sick children were mixed, (4) average data obtained on groups of patients were mixed with data obtained on individual patients, and (5) results obtained using investigative techniques that may have altered the outcome of the respective studies were considered. Consequently, many of these reviews draw conclusions that may be incorrect. The aim of the present review was to provide a comprehensive and updated overview of the available original data on the ontogeny of GI luminal conditions relevant to oral drug absorption in the paediatric population. To this end, the PubMed and Web of Science metadatabases were searched for appropriate studies that examined age-related conditions in the oral cavity, esophagus, stomach, small intestine, and colon. Maturation was observed for several GI parameters, and corresponding data sets were identified for each paediatric age group. However, it also became clear that the ontogeny of several GI traits in the paediatric population is not yet known. The review article provides a robust and valuable data set for the development of paediatric in vitro and in silico biopharmaceutical tools to support the development of age-appropriate dosage forms. In addition, it provides important information on existing data gaps and should provide impetus for further systematic and well-designed in vivo studies on GI physiology in children of specific age groups in order to close existing knowledge gaps and to sustainably improve oral drug therapy in children.

Circadian clocks in the digestive system

Many molecular, physiological and behavioural processes display distinct 24-hour rhythms that are directed by the circadian system. The master clock, located in the suprachiasmatic nucleus region of the hypothalamus, is synchronized or entrained by the light-dark cycle and, in turn, synchronizes clocks present in peripheral tissues and organs. Other environmental cues, most importantly feeding time, also synchronize peripheral clocks. In this way, the circadian system can prepare the body for predictable environmental changes such as the availability of nutrients during the normal feeding period. This Review summarizes existing knowledge about the diurnal regulation of gastrointestinal processes by circadian clocks present in the digestive tract and its accessory organs. The circadian control of gastrointestinal digestion, motility, hormones and barrier function as well as of the gut microbiota are discussed. An overview is given of the interplay between different circadian clocks in the digestive system that regulate glucose homeostasis and lipid and bile acid metabolism. Additionally, the bidirectional interaction between the master clock and peripheral clocks in the digestive system, encompassing different entraining factors, is described. Finally, the possible behavioural adjustments or pharmacological strategies for the prevention and treatment of the adverse effects of chronodisruption are outlined.

Clinical applications of gastrointestinal manometry in children

Manometry is a noninvasive diagnostic tool for identifying motility dysfunction of the gastrointestinal tract. Despite the great technical advances in monitoring motility, performance of the study in pediatric patients has several limitations that should be considered during the procedure and interpretation of the test results. This article reviews the clinical applications of conventional esophageal and anorectal manometries in children by describing a technique for performing the test. This review will develop the uniformity required for the methods of performance, the parameters for measurement, and interpretation of test results that could be applied in pediatric clinical practice.

Effect of different pH criteria on dual-sensor pH monitoring in the evaluation of supraesophageal gastric reflux in children

BACKGROUND AND AIM

Existing tests for supraesophageal gastric reflux (SEGR) that focus on pH drops <4 in the proximal esophagus have had limited sensitivity and specificity. The aim of the present study was to evaluate the effect of newly proposed pH criteria on SEGR detection.

PATIENTS AND METHODS

Twenty-four-hour dual-sensor pH tracings of 32 patients were reviewed. Proximal esophageal pH data were evaluated according to the conventional definition of pH drop <4 and 2 proposed definitions: pH drop <5.5 while upright and <5.0 while supine and pH drop of >10% from a running baseline. For each potential SEGR event, the preceding 1-minute window was examined for corresponding distal acid reflux.

RESULTS

Of the 542 distal acid reflux events detected, 200 were associated with a proximal pH drop <4; this number increased to 295 using the definition of proximal pH drop <5.5 (upright)/<5.0 (supine) and 301 using the definition of proximal pH drop >10%. A proportion of proximal events, however, was not associated with distal acid reflux: 21 of 200 (10.5%) proximal pH <4 events, 119 of 414 (29%) proximal pH <5.5 (upright)/<5.0 (supine) events, and 272 of 573 (47%) proximal pH drop >10% events lacked a preceding or simultaneous drop in distal pH <4.

CONCLUSIONS

Although the use of more liberal pH criteria increased the diagnostic yield for SEGR events with dual-sensor monitoring, a significant proportion of proximal pH events did not correlate with distal acid reflux. These events could represent either false-positive measurements or association with weakly acid reflux.

Esophageal dysmotility in children with eosinophilic esophagitis: a study using prolonged esophageal manometry

OBJECTIVES

The pathophysiology of dysphagia in patients with eosinophilic esophagitis (EoE) is unknown but may be related to abnormal esophageal motor function. Symptoms rarely occur during stationary esophageal manometry, so it has been difficult to establish an association between symptoms and motor events. Our aim was to evaluate esophageal motor function in children with EoE with the use of stationary manometry and ambulatory prolonged esophageal manometry and pH-metry (PEMP).

METHODS

PEMP was performed in children with EoE and compared with controls and children with gastroesophageal reflux disease (GERD). Peristalsis was considered effective when the esophageal contractions had a normal amplitude and propagation. Results are expressed as mean+/-s.e.

RESULTS

Seventeen patients with EoE, 13 with GERD, and 11 controls were studied. Values are expressed as mean+/-s.e. Stationary manometry identified abnormal peristalsis in 41% of children with EoE. During PEMP, children with EoE had an increased number of isolated (16.7+/-3.8 vs. 9.5+/-1.6 vs. 6.5+/-1.1; P<0.03) and high-amplitude contractions (4.1+/-1.2 vs. 1.8+/-0.8 vs. 0.1+/-0.1; P<0.03), and higher percentage ineffective peristalsis both during fasting (70.5%+/-2.5 vs. 57.8%+/-3.0 vs. 53.8%+/-1.9; P<0.05) and during meals (68.4+/-3.4 vs. 55.3+/-2.8 vs. 48.1+/-2.8; P<0.05) when compared with children with GERD and controls. Thirteen patients with EoE experienced 21 episodes of dysphagia, and all correlated with simultaneous abnormal motor function.

CONCLUSIONS

PEMP allowed the detection of ineffective peristalsis in children with EoE. Symptoms observed in children with EoE may be related to esophageal motor dysfunction.

The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms

OBJECTIVES

Previous evidence suggests an association between gastroesophageal reflux disease and chronic respiratory disease in children. Despite antisecretory antacid therapy, respiratory symptoms often persist supporting a role for nonacid reflux. The aim of this study was to determine whether nonacid reflux occurs in children with chronic respiratory disease.

METHODS

Twenty-eight children (mean age: 6.5 +/- 5.6 yr) with persistent respiratory symptoms on antacid medications underwent 24 h pH/multichannel intraluminal impedance (pH/MII) recording. The symptom index (SI) and the symptom sensitivity index (SSI) were calculated for each patient. Logistic regression was performed to determine which reflux characteristics were associated with a high degree of symptom correlation present during the occurrence of symptoms.

RESULTS

A total of 1,822 reflux episodes were detected by pH/MII, 45% of which were nonacidic. The mean SI increased using pH/MII (35.7 +/- 28.5) compared to pH probe alone (14.6 +/- 18.9; p= 0.002); no differences in the mean SSI using pH/MII compared to pH probe alone were identified. Significantly more patients had a positive SI using pH/MII than pH probe alone (p= 0.035); there was no difference in the number of patients with a positive SSI using pH/MII compared to pH probe alone. Multivariate analysis revealed that symptoms occurred more frequently when the reflux was nonacidic, mixed, and full column. Also, younger children were more likely to have the simultaneous occurrence of symptoms and reflux.

CONCLUSIONS

Nonacid reflux may be an important predictor of respiratory symptoms. pH/MII provided important information in the evaluation of children with intractable respiratory symptoms.